This invention relates to a method for manufacturing a chip capacitor, e.g. a chip-type tantalum capacitor.
Japanese Examined Patent Publication (KOKOKU) No. SHO 55-47449 B2 published on Nov. 29, 1980 and Japanese Examined Patent Publication (KOKOKU) No. HEI 1-29050 B2 published on Jun. 7, 1989, both of which are owned by the assignee of the present application, disclose a method of manufacturing chip-type tantalum capacitors.
A According to the method disclosed in Japanese Examined Patent Publication No. SHO 55-47449 B2, a terminal frame including pairs of cathode and anode terminal portions disposed spaced from each other along a line are arranged in rows and columns is prepared. Capacitor elements each including a cathode layer disposed to cover the outer surface of the capacitor element and an anode lead extending from one end thereof are prepared. The cathode layer of each capacitor element is connected to the cathode terminal portion of an associated one of the cathode-anode terminal portion pairs of the terminal frame, with the anode lead of that capacitor element connected to the anode terminal portion in the same pair. Then, all the capacitor elements, the cathode terminal portions and the anode terminal portions in respective rows are molded in a resin. Thus, the cathode and anode terminal portions except those portions connected to the frame are embedded in the resin. After that, the cathode and anode terminal portions are separated from the terminal frame, and, also, the resin is cut along lines between adjacent ones of the capacitor elements to thereby complete chip-type capacitors.
According to a method disclosed in Japanese Examined Patent Publication No. HEI 1-29050 B2, chip-type capacitors are manufactured by punching plural pairs of generally rectangular anode and cathode terminal portions arranged in line in an electrically conductive metal sheet, with an opening disposed between each pair of anode and cathode terminal portions. The anode and cathode terminal portions are pushed upright with the bases of the respective terminal portions connected to the metal sheet. Respective sides of the raised rectangular terminal portions are inwardly bent. Capacitor elements are disposed between respective pairs of raised terminal portions. Metal chips welded on tip ends of anode leads of respective capacitor elements are connected to inner surfaces of respective ones of the inwardly bent anode terminal portions, and cathode layers disposed on outer surfaces of respective ones of the capacitor elements are connected to inner surfaces of respective ones of the inwardly bent cathode terminal portions. Resin is placed in the spaces between respective anode and cathode terminal portion pairs to cover the capacitor elements disposed between them. After that, the anode and cathode terminal portions are separated from the conductive metal sheet to complete chip-type capacitors.
According to Japanese Examined Patent Publication SHO 55-47449 B2, resin molding is provided for each row of capacitor elements. In addition, since the cathode and anode terminal portions are embedded in the resin, they occupy a relatively large amount of the volume of the chip capacitor mold, which impedes downsizing of such chip capacitor.
According to Japanese Examined Patent Publication No. HEI 1-29050, both anode and cathode terminal portions have parts located below the capacitor element. However, since the anode terminal is at a location remote from the cathode layer, it is not possible to reduce the length of the chip capacitor.
Therefore, an object of the present invention is to provide a method of manufacturing chip capacitors in a small size.
According to one embodiment of the present invention, a terminal frame is first prepared. The terminal frame includes plural pairs of terminal sections arranged in rows and columns. Each terminal section pair includes a flat anode terminal section and a flat cathode terminal section, which are arranged in the same plane with their tip ends facing to each other with a spacing disposed between them. The terminal frame may be formed by etching or punching an electrically conductive material, e.g. a metal sheet or metal foil.
A plurality of capacitor elements are prepared. Each capacitor element includes a cathode layer covering the outer surface of the capacitor element, and an anode lead extending outward from the element. The cathode layer includes a flat surface portion at least in its bottom surface. The capacitor element may have a shape of generally rectangular parallelepiped or a semicylindrical shape. At least the bottom surface of the capacitor element is flat. The cathode layer is present also on this flat bottom surface. The anode lead extends out of an end of the capacitor element and may be columnar or planar in shape. Alternatively, it may have a shape of foil.
One such capacitor element is disposed in association with each terminal section pair. Then, the anode lead of the capacitor element is electrically and mechanically connected to first one of major surfaces of the anode terminal section of the terminal section pair. The cathode layer of the capacitor element is connected to a first major surface of the cathode terminal section of the same terminal section pair which is located in substantially the same plane as the first major surface of the anode terminal section. Then, the terminal frame and the capacitor elements mounted on it are entirely covered with a resin so as to embed all of the capacitor elements, leaving exposed at least a portion of the second, opposite major surface of each anode terminal section and at least a portion of the second, opposite major surface of each cathode terminal section, to thereby form a capacitor assembly of chip capacitors each including a capacitor element having an anode lead and a cathode layer connected to associated anode and cathode terminal sections and a resin coating covering them. The covering may be carried out by means of a molding machine capable of molding the entire terminal frame and all of the capacitor elements, e.g. a transfer mold machine with a cavity capable of accommodating the terminal frame in its entirety, or a screen printing machine, or an injection mold machine. The capacitor assembly is cut, by means of, for example, a dicing machine, into individual chip capacitors.
The capacitor assembly may be separated into individual chip capacitors by forming slits having a width between adjacent chip capacitors of the capacitor assembly. If the capacitor assembly is separated by forming single thin cut lines in the terminal frame between adjacent chip capacitors, a larger amount of resin will be left on the resulting individual chip capacitors, so that the chip capacitors cannot be small in size. By separating the capacitor assembly by forming slots with some width, the amount of resin to be left on the resulting chip capacitors can be reduced, which helps further downsizing of chip capacitors.
When disposing respective capacitor elements in association with anode and cathode terminal sections, an insulator may be disposed on the tip end of each anode terminal section, and the cathode layer of each capacitor element is placed in contact with the tip end of the associated anode terminal section and with the associated cathode terminal section. The insulator may be an insulating tape or insulating paint, e.g. insulating ink. In addition, the proximal end of each anode terminal section may be disposed in the vicinity of the tip end of the anode lead of the associated capacitor element.